1. Field
The present disclosure generally relates to a wavelength division multiplexing-passive optical network (hereinafter, referred to as “WDM-PON”) system, and more specifically, to a WDM-PON system configured to multiplex and divide laser lights having various wavelengths each having the same intensity in a central office to supply the laser lights to subscribers so that several subscribers share a light source having the same wavelength.
2. Discussion of the Related Technology
As the information society is moved into, people are keenly concerned to a WDM-PON configured to connect an optical line directly to a subscriber terminal so as to supply various wideband multimedia services to a plurality of subscribers. The WDM-PON refers to a network configured to connect an interval between an optical line terminal (hereinafter, referred to as “OLT”) and an optical network unit (hereinafter, referred to as “ONU”) with a passive optical device and to transmit optical signals having multiplexed letters/audio/video data into each ONU. The WDM-PON can provide information of large capacity to subscribers with excellent security and performance.
FIG. 1 is a diagram illustrating a WDM-PON system.
In the WDM-PON system of FIG. 1, when a central office provides a light source (Σλis) of a predetermined intensity in different wavelengths for each subscriber, a WDM multiplexer/demultiplexer (hereinafter, referred to as “WDM MD”) located in a remote node of a subscriber demultiplexes wavelengths of light sources in each subscriber and transmits the demultiplexed light source into the ONU. The light source λis having the demultiplexed wavelength is modulated by projecting the light into a reflective optical amplifier of the ONU and amplifying or absorbing the light depending on input current of the optical amplifier. A modulated subscriber optical signal λim is multiplexed in the WDM MD (Σλim) and transmitted into the central office.
However, in the WDM-PON system, light sources having the same wavelength cannot be used by several subscribers since an optical signal (a downward optical signal) is used to generate a subscriber optical signal (upward optical signal) (λim). As a result, a light source between the central office and the ONU and a wavelength of optical signals are different in each subscriber, and a large amount of resources (wavelengths) is required to embody the above-described system in an optical subscriber network to admit a large number of subscribers, thereby requiring great cost.
The foregoing discussion in this section is to provide general background information, and does not constitute an admission of prior art.